Disclosed is a road speed limit identification method. The road speed limit identification method includes: obtaining a driving image captured during driving of a moving object; setting a region of interest in the obtained driving image and generating a grayscale-processed image on the basis of an image of the region of interest; detecting a speed limit sign image from the grayscale-processed image; calculating a first brightness value of a number region, a second brightness value of a border region, and a third brightness value of an in-border region other than the number region in the detected speed limit sign image; and identifying a speed limit displayed on a speed limit sign on the basis of the plurality of calculated brightness values.